Former alliance director Arnaud Deboeuf will become PSA's industrial strategy director under Chief Executive Carlos Tavares, himself a former Renault second-in-command, the rival French carmaker confirmed on Tuesday.

Deboeuf's exit underscores deep tensions threatening to subsume the Renault-Nissan alliance in the wake of the November 2018 arrest of former Chairman Carlos Ghosn, now awaiting trial in Japan on financial misconduct charges he denies.

Those tensions have been exacerbated by failed attempts under Bollore and new Renault Chairman Jean-Dominique Senard to secure a full Renault-Nissan merger and to combine Renault with Fiat Chrysler, a move thwarted by the French state.

Deboeuf was well regarded at Nissan and even offered a senior executive role at the Japanese carmaker, as his relations with Bollore soured following Ghosn's ouster, three sources told Reuters. But Bollore, a former Ghosn protégé who succeeded his absent boss as CEO in January, blocked the move.

"Thierry Bollore told me no one wanted to work with me ... and that I could not go to work at Nissan either," Deboeuf said in a farewell email to colleagues seen by Reuters.

Renault declined to comment on Deboeuf's departure. Deboeuf did not respond to requests for comment.

His move adds to a steady Renault brain-drain to PSA since 2013, when Tavares was hired to rescue the carmaker from near-bankruptcy. Other switchers from Renault include Yann Vincent, PSA's executive vice president for manufacturing, and powertrain engineering chief Alain Raposo.

Tavares, who preceded Bollore as Ghosn's No.2 at Renault, was pushed out after publicly voicing CEO ambitions. Under its Portuguese-born leader, PSA has set new profitability records while making swift headway on the integration of Opel, acquired from General Motors in 2017. (Reporting by Gilles Guillaume and Laurence Frost, Editing by Richard Lough and Mark Potter)